OAKLAND — A track problem briefly delayed BART service through the Transbay Tube Monday, but the system is recovering now and the transit says there is a 20-minute delay in service between the Embarcadero and West Oakland stations.

The cause of what was called unscheduled maintenance was not specified.

Violent police encounters in California last year led to the deaths of 157 people and six officers, the state attorney general’s office said Thursday in a report that provides the first statewide tally on police use-of-force incidents.